Head to head
Crocodile Monitor vs Komodo Dragon
The crocodile monitor and the Komodo dragon are both huge members of the monitor lizard genus Varanus, both from the islands of Southeast Asia and Australasia, both with forked tongues, serrated teeth, and venom glands. They are often set against each other for the title of largest lizard, and the answer depends on whether largest means longest or heaviest.
| Crocodile Monitor | Komodo Dragon | |
|---|---|---|
| Scientific name | Varanus salvadorii | Varanus komodoensis |
| Where it lives | Lowland rainforest of New Guinea | A few islands in Indonesia |
| Record it holds | The longest lizard | The heaviest and most massive lizard |
| Length | About 2.5 m verified, mostly tail | About 3 m |
| Weight | Around 20 kg | About 70 to 90 kg, record 166 kg |
| Build and lifestyle | Slender; tree-dwelling climber | Stocky; ground-dwelling ambush hunter |
| Main prey | Birds, eggs, bats, small mammals | Deer, wild pigs, water buffalo, carrion |
| Conservation status | Least Concern (data poor) | Endangered |
Crocodile Monitor vs Komodo Dragon: common questions
Which is bigger, the crocodile monitor or the Komodo dragon?
It depends on how you measure. By length the crocodile monitor usually wins, with verified animals around 2.5 metres and credible historical claims of more, which is why it is generally called the longest lizard in the world. By weight and bulk the Komodo dragon wins overwhelmingly, weighing 70 to 90 kilograms against the crocodile monitor's roughly 20, and being far more heavily built through the head, neck, and body. The reason for the split is the tail: about two thirds of a crocodile monitor's total length is a long, thin, whip-like tail, so a great deal of its length carries very little mass. The fairest summary is that the crocodile monitor is the longest lizard and the Komodo dragon is the largest and heaviest.
Are both of these lizards venomous?
Yes, in the sense that both have venom glands in the lower jaw, a discovery made across the monitor lizards and their relatives in 2009 that overturned the earlier idea that Komodo dragons killed by infecting prey with dirty-mouthed bacteria. The venom of the Komodo dragon lowers blood pressure and prevents blood from clotting, so a bitten deer or pig suffers rapid blood loss and shock and can be tracked down as it weakens. The role of venom in the crocodile monitor is far less studied, but it is thought to have a similar function against birds and mammals. In practice, for prey the size of a person the immediate danger from either species is the bite itself, from powerful jaws lined with sharp, serrated, backward-hooked teeth, and the tearing wounds and infection that follow.
Why is the Komodo dragon endangered but the crocodile monitor not?
Mostly because of range and how well each is known. The Komodo dragon exists only on a handful of small Indonesian islands, with a total wild population of a few thousand, and that tiny, concentrated range makes it highly vulnerable to habitat loss, declines in its prey, tourism pressure, and, in the longer term, rising sea levels shrinking its low-lying habitat, which is why it was moved to Endangered in 2021. The crocodile monitor has a much larger range across the whole island of New Guinea, and although it is hunted locally and taken for the pet trade and its forest is being cleared, there is no evidence of a steep overall decline, and it is listed as Least Concern. That listing partly reflects genuine security and partly reflects how little fieldwork has been done on such a secretive rainforest animal.